In recent years, a mobile communication system to which “EUL (Enhanced Uplink)” is applied in a radio uplink has been studied in the 3GPP.
As shown in FIG. 1, in the mobile communication system, an enhanced dedicated physical data channel (E-DPDCH), an enhanced dedicated physical control channel (E-DPCCH), a dedicated physical data channel (DPDCH), and a dedicated physical control channel (DPCCH) are transmitted in an uplink.
Here, the hybrid ARQ (Auto Repeat reQuest), which is a kind of retransmission control processings, is applied to the enhanced dedicated physical data channel (E-DPDCH).
In the mobile communication system, a mobile station UE is configured to constantly transmit the dedicated physical data channel (DPDCH) and the dedicated physical control channel (DPCCH) at a predetermined cycle.
In other words, the mobile station UE is configured to transmit the dedicated physical data channel (DPDCH) in a transmission format (in which a transmission data block size is “0”) containing a control header and a CRC error detection code (for example, 10 bits, 12 bits, 16 bits, 24 bits or the like) only, when there is no transmission data block that should be transmitted.
On the other hand, the mobile station UE is configured to intermittently transmit the enhanced dedicated physical data channel (E-DPDCH) and the enhanced dedicated physical control channel (E-DPCCH) only when there is transmission data block that should be transmitted.
Additionally, a radio base station Node B is configured to determine transmission power control information (a TPC command) and to notify the mobile station UE of the transmission power control information. Here, the transmission power control information is used for controlling the transmission power of a dedicated physical control channel (DPCCH) in the mobile station UE, so that a reception quality of the dedicated physical control channel (DPCCH) can satisfy a target SIR by a closed-loop power control based on a reception power of the dedicated physical control channel (DPCCH) constantly transmitted from the mobile station UE.
Furthermore, the radio base station Node B is configured to adjust the abovementioned target SIR of the dedicated physical control channel (DPCCH) by an outer-loop power control based on a reception power of a dedicated physical data channel (DPDCH) constantly transmitted from the mobile station UE.
Note that the mobile station UE is configured: to transmit the enhanced dedicated physical data channel (E-DPDCH) with a transmission power having an E-DPDCH offset relative to a transmission power of the dedicated physical control channel (DPCCH); to transmit the enhanced dedicated physical control channel (E-DPCCH) with a transmission power having an E-DPCCH offset relative to a transmission power of the dedicated physical control channel (DPCCH); and to transmit the dedicated physical data channel (DPDCH) with a transmission power having a DPDCH offset relative to a transmission power of the dedicated physical control channel (DPCCH).
However, the conventional mobile communication system as described above has a problem of requiring an unnecessary equipment cost, because, even in a case where the mobile station UE transmits all of transmission data blocks by using the enhanced dedicated physical data channel (E-DPDCH), a function (for example, a dedicated physical data channel (DPDCH) despreader, or the like) of receiving the dedicated physical data channel (DPDCH) should be provided in the radio base station Node B, in order to stabilize a communication quality when there is no transmission data block that should be transmitted.
[Non-patent Document 1] “W-CDMA Mobile Communication Systems”, edited by Keiji Tachikawa (Maruzen Co., Ltd.)
[Non-patent Document 2] 3GPP TR25.896 v6.0.0